Metabolic alterations in patients with Parkinson disease and visual hallucinations

Background: Visual hallucinations ( VHs) occur frequently in advanced stages of Parkinson disease ( PD). Which brain regions are affected in PD with VH is not well understood. Objectives: To characterize the pattern of affected brain regions in PD with VH and to determine whether functional changes in PD with VH occur preferentially in visual association areas, as is suggested by the complex clinical symptomatology. Design: Positron emission tomography measurements using fluorodeoxyglucose F 18. Between-group statistical analysis, accounting for the variance related to disease stage. Setting: University hospital. Patients: Eight patients with PD and VH and 11 patients with PD without VH were analyzed. The presence of VH during the month before positron emission tomography was rated using the Neuropsychiatric Inventory subscale for VH ( PD and VH, 4.63; PD without VH, 0.00; P < .002). Results: Parkinson disease with VH, compared with PD without VH, was characterized by reduction in the regional cerebral metabolic rate for glucose consumption ( P < .05, corrected for false discovery rate) in occipito-temporoparietal regions, sparing the occipital pole. No significant increase in regional glucose metabolism was detected in patients with PD and VH. Conclusions: The pattern of resting-state metabolic changes in regions of the dorsal and ventral visual streams, but not in primary visual cortex, in patients with PD and VH, is compatible with the functional roles of visual association areas in higher-order visual processing. These findings may help to further elucidate the functional mechanisms underlying VH in PD.